Iodine-containing photoacid generators and compositions comprising the same

ABSTRACT

A photoacid generator compound having formula (I): 
     
       
         
         
             
             
         
       
         
         wherein, in formula (I), groups and variables are the same as described in the specification.

FIELD

The present disclosure generally relates to polymer compositionsincluding a photoacid generator. Specifically, the disclosure providescopolymers derived from a monomer including at least two iodine atoms.

BACKGROUND

Extreme ultraviolet lithography (“EUVL”) is one of the leadingtechnology options to replace optical lithography for volumesemiconductor manufacturing at feature sizes <20 nm. The extremely shortwavelength (13.4 nm) is a key enabling factor for high resolutionrequired at multiple technology generations. In addition, the overallsystem concept scanning exposure, projection optics, mask format, andresist technology—is quite similar to that used for current opticaltechnologies. Like previous lithography generations, EUVL consists ofresist technology, exposure tool technology, and mask technology. Thekey challenges are EUV source power and throughput. Any improvement inEUV power source will directly impact the currently strict resistsensitivity specification. Indeed, a major issue in EUVL imaging isresist sensitivity, the lower the sensitivity, the greater the sourcepower that is needed or the longer the exposure time that is required tofully expose the resist. The lower the power levels, the more noiseaffects the line edge roughness (“LER”) of the printed lines.

It has been shown that EUV light absorption cross-section and secondaryelectron generation yield are critical factors for EUV sensitivity. Oneway to increase EUV photoresist sensitivity is by increasing itsabsorption cross-section at 13.5 nm, which is an atomic property of thematerial that can be theoretically calculated using known atomicabsorptions. Typical atoms that make up resist materials, such ascarbon, oxygen, hydrogen, and nitrogen possess very weak absorption at13.5 nm. A fluorine atom has slightly higher absorption and has beenused in the search for high EUV absorbing photoresist.

Iodine has remarkably high absorption cross-section at EUV radiation.Recent patent publication JP 2015-161823 discloses iodine-containingmonomers and corresponding polymers useful for lithographic processing.However, the publication does not disclose an iodine-containing smallmolecule photoacid-generators. There is still a need for iodine-richresist components that possess good solubility and that imparts improvedsensitivity under EUV exposure.

SUMMARY

An embodiment provides a photoacid generator compound having formula(I):

wherein, in formula (I):

“I” represents iodine;

V is OR¹ or C(═O)OR¹, wherein R¹ is independently H or a substituted orunsubstituted C₁₋₃₀ hydrocarbyl group optionally comprising 1 to 5heteroatoms selected from O, S, N, P, and F, and optionally comprisingan acid-cleavable group, a polymerizable group, or a combinationthereof;

W is a single bond or a group selected from —(C═O)O—, —O(C═O)—,—O(SO₂)—, —(SO₂)O—, —NH(SO₂)—, —(SO₂)NH—, —NH(CO)—, —(CO)NH—, —SO₂—, and—SO—;

m is an integer of 0 or greater;

n is an integer of 0 or greater;

L is a single bond or a group selected from a substituted orunsubstituted C₁₋₂₀ alkylene group, a substituted or unsubstituted C₁₋₂₀heteroalkylene group, a substituted or unsubstituted C₃₋₂₀ cycloalkylenegroup, and a substituted or unsubstituted C₃₋₂₀ heterocycloalkylenegroup, a substituted or unsubstituted C₆₋₂₀ arylene group, and asubstituted or unsubstituted C₇₋₂₀ aralkylene group;

represents a monocyclic or polycyclic unsubstituted or substituted C₆₋₃₀arylene group or a monocyclic or polycyclic unsubstituted or substitutedC₃₋₃₀ heteroarylene group, wherein each “*” indicates a point ofattachment to a neighboring group or atom;

G⁺ has formula (II):

wherein, in formula (II):

X is S or I,

each R^(c) is unsubstituted or substituted, halogenated ornon-halogenated and is independently a C₁₋₃₀ alkyl group; a polycyclicor monocyclic C₃₋₃₀ cycloalkyl group; a polycyclic or monocyclic C₄₋₃₀aryl group,

wherein when X is S, one of the R^(c) is optionally attached to oneadjacent R^(c) to form a ring,

wherein when X is I, n is an integer of 1 or greater,

wherein when X is S, n is an integer of 0 or greater, provided thephotoacid generator having formula (I) comprises at least two iodineatoms,

z is 2 or 3, wherein when X is I, z is 2, or when X is S, z is 3; and

Y is SO₃, CO₂, NHSO₃, or O.

Another embodiment provides a photoresist composition compound includingthe photoacid generator compound and a copolymer.

Yet another embodiment provides a method of forming an electronicdevice, comprising:

-   -   (a) applying a layer of the photoresist composition of claim 7        or 8 over a surface of the substrate;    -   (b) pattern-wise exposing the photoresist composition layer to        activating radiation; and    -   (c) developing the exposed photoresist composition layer to        provide a resist relief image.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, advantages, and features of this disclosurewill become more apparent by describing in further detail exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a scheme showing synthesis of the photoacid generatordesignated ECPPDBT TIP-TFBA;

FIG. 2 is a scheme showing synthesis of the photoacid generatordesignated IPDPS PFBuS;

FIG. 3 is a scheme showing synthesis of the photoacid generatordesignated as IPDPS PFBuS;

FIG. 4 is a scheme showing synthesis of the photoacid generatordesignated as DTBPI 4IP-TFBS; and

FIG. 5 shows structures of photoacid generator compounds PAG1 to PAG4and polymer P1 described in the working examples of the presentapplication.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. In this regard,the present exemplary embodiments may have different forms and shouldnot be construed as being limited to the descriptions set forth herein.Accordingly, the exemplary embodiments are merely described below, byreferring to the figures, to explain aspects of the present description.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

It will be understood that when an element is referred to as being “on”another element, it can be directly in contact with the other element orintervening elements may be present therebetween. In contrast, when anelement is referred to as being “directly on” another element, there areno intervening elements present.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers, and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another element, component, region, layer, orsection. Thus, a first element, component, region, layer, or sectiondiscussed below could be termed a second element, component, region,layer, or section without departing from the teachings of the presentembodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

As used herein, when a definition is not otherwise provided, the term“alkyl group” refers to a group derived from a straight or branchedchain saturated aliphatic hydrocarbon having the specified number ofcarbon atoms and having a valence of at least one.

As used herein, when a definition is not otherwise provided, the term“fluoroalkyl group” refers to an alkyl group in which one or morehydrogen atoms are replaced with fluorine atoms.

As used herein, when a definition is not otherwise provided, the term“alkoxy group” refers to “alkyl-O—”, wherein the term “alkyl” has thesame meaning as described above.

As used herein, when a definition is not otherwise provided, the term“fluoroalkoxy group” refers to an alkoxy group in which one or morehydrogen atoms are replaced with fluorine atoms.

As used herein, when a definition is not otherwise provided, the term“cycloalkyl group” refers to a monovalent group having one or moresaturated rings in which all ring members are carbon.

As used herein, when a definition is not otherwise provided, the term“alkenyl group” refers to a straight or branched chain, monovalenthydrocarbon group having at least one carbon-carbon double bond.

As used herein, when a definition is not otherwise provided, the term“alkenylalkyl group” refers to “alkenyl-alkyl-”, wherein the terms“alkenyl” and “alkyl” have the same meaning as described above.

As used herein, when a definition is not otherwise provided, the term“alkynyl group” refers to a straight or branched chain, monovalenthydrocarbon group having at least one carbon-carbon triple bond.

As used herein, when a definition is not otherwise provided, the term“alkynylalkyl group” refers to “alkynyl-alkyl-”, wherein the terms“alkynyl” and “alkyl” have the same meaning as described above.

As used herein, when a definition is not otherwise provided, the term“aryl”, which is used alone or in combination, refers to an aromatic orheteroaromatic hydrocarbon containing at least one ring and having thespecified number of carbon atoms. The term “aryl” may be construed asincluding a group with an aromatic or heteroaromatic ring fused to atleast one cycloalkyl or heterocycloalkyl ring. The “aryl” group mayinclude one or more heteroatom(s) independently selected from nitrogen(N), oxygen (O), P (phosphorus), and sulfur (S).

As used herein, when a definition is not otherwise provided, the term“aryloxy group” refers to “aryl-O—”, wherein the term “aryl” has thesame meaning as described above.

As used herein, when a definition is not otherwise provided, the term“aralkyl group” refers to a substituted or unsubstituted aryl groupcovalently linked to an alkyl group that is linked to a compound.

As used herein, when a definition is not otherwise provided, the term“alkylene group” refers to a straight or branched saturated aliphatichydrocarbon group having a valence of at least two, optionallysubstituted with one or more substituents where indicated, provided thatthe valence of the alkylene group is not exceeded.

As used herein, when a definition is not otherwise provided, the term“cycloalkylene group” refers to a cyclic hydrocarbon group having avalence of at least two, optionally substituted with one or moresubstituents where indicated, provided that the valence of thecycloalkylene group is not exceeded.

As used herein, when a definition is not otherwise provided, the term“arylene group” refers to a functional group having a valence of atleast two obtained by removal of two hydrogens in an aromatic ring,optionally substituted with one or more substituents where indicated,provided that the valence of the arylene group is not exceeded.

As used herein, when a definition is not otherwise provided, the term“aralkylene group” refers to a functional group having a valence of atleast two obtained by removal of two hydrogens from thealkyl-substituted aromatic compound, optionally substituted with one ormore substituents where indicated, provided that the valence of thearalkylene group is not exceeded.

As used herein, when a definition is not otherwise provided, the term“heteroarylene group” refers to a functional group having a valence ofat least two obtained by removal of two hydrogens in a heteroaromaticring, optionally substituted with one or more substituents whereindicated, provided that the valence of the heteroarylene group is notexceeded.

As noted above, one way for increasing the sensitivity in EUVlithography is to increase the absorption cross-section of the resistcomposition at 13.5 nm. Enhancing chemically amplified resistsabsorption at EUV wavelength require the incorporating highly absorbingelements. The atomic absorption cross-sections at EUV of elements areknown in the literature (see for example: Fallica R. et al. SPIEAdvanced Lithography, 977612, 2016) and references cited therein). Theelemental make up of molecules and polymers used in organic chemicallyamplified resists are mostly limited to carbon, hydrogen, oxygen andnitrogen. These elements have exceptionally low absorption at 13.5 nm.Fluorine atom has slightly higher absorption at 13.5 nm compared tooxygen atom. Christianson et al. explore the incorporation of fluorineatoms onto polymers backbone (see Christianson et al., SPIE AdvancedLithography 868216, 2013). The iodine atom has remarkably higherabsorption cross-section at EUV. The inventors of the present inventiondiscovered small molecules photoacid generators that include at leastone aryl group substituted with one or more iodine atoms, preferably twoor more iodine atoms, wherein the iodine-substituted aryl group may be apart of the photoacid generator cation, photoacid generator anion, orboth.

An embodiment of the present disclosure provides a photoacid generatorcompound having formula (I):

In formula (I),

“I” represents iodine, and

(hereinafter “G”) represents a monocyclic or polycyclic unsubstituted orsubstituted C₆₋₃₀ arylene group or a monocyclic or polycyclicunsubstituted or substituted C₃₋₃₀ heteroarylene group, wherein each “*”indicates a point of attachment to a neighboring group or atom.

Variable n defining a number of iodines in

may be an integer of 0 or greater. For example, variable n may be aninteger of 1 or greater. Accordingly, there may be at least one iodineatom attached to the moiety “G”. In an embodiment, “G” may be a C₆ arylgroup, and n may be 1, 2, 3, 4, or 5.

Variable m defining a number of groups V may be an integer of 0 orgreater. When m is 0, group V is absent and hydrogen is present at thepoint of connection to the moiety “G”. When m is greater than 0, V maybe OR¹ or C(═O)OR¹, wherein R¹ is independently H or a substituted orunsubstituted C₁₋₃₀ hydrocarbyl group optionally comprising 1 to 5heteroatoms selected from O, S, N, P, and F, and optionally comprisingan acid-cleavable group, a polymerizable group, or a combinationthereof. As used herein, the term “acid-cleavable group” refers to agroup that is hydrolyzed by the action of an acid. Such acid-cleavablegroups are well-known to one of ordinary skill in the art. In anembodiment, the acid-cleavable group may be (i) a tertiary C₁₋₃₀ alkoxy(for example, a tert-butoxy group), a tertiary C₃₋₃₀ cycloalkoxy group,a tertiary C₁₋₃₀ fluoroalkoxy group, (ii) a tertiary C₃₋₃₀alkoxycarbonylalkyl group, a tertiary C₅₋₃₀ cycloalkoxycarbonylalkylgroup, a tertiary C₃₋₃₀ fluoroalkoxycarbonylalkyl group, (iii) atertiary C₃₋₃₀ alkoxycarbonylalkoxy group, a tertiary C₅₋₃₀cycloalkoxycarbonylalkoxy group, a tertiary C₃₋₃₀fluoroalkoxycarbonylalkoxy group, or (iv) a C₂₋₃₀ acetal group includingmoiety —O—C(R¹¹R¹²)—O— (wherein R¹¹R¹² are each independently hydrogenor a C₁₋₃₀ alkyl group).

W may be a single bond or a group selected from —(C═O)O—, —O(C═O)—,—O(SO₂)—, —(SO₂)O—, —NH(SO₂)—, —(SO₂)NH—, —NH(CO)—, —(CO)NH—, —SO₂—, and—SO—. When W is a single bond, groups L and “G” are connected to eachother by a single bond, and no intermediate group is present in between.In an embodiment, W may be a single bond or —(C═O)O—.

L may be a single bond or a divalent group selected from a substitutedor unsubstituted C₁₋₂₀ alkylene group, a substituted or unsubstitutedC₁₋₂₀ heteroalkylene group, a substituted or unsubstituted C₃₋₂₀cycloalkylene group, and a substituted or unsubstituted C₃₋₂₀heterocycloalkylene group, a substituted or unsubstituted C₆₋₂₀ arylenegroup, and a substituted or unsubstituted C₇₋₂₀ aralkylene group. When Lis a single bond, groups Y and W are connected to each other by a singlebond, and no intermediate group is present in between. In an embodiment,L may be a single bond or a group having formula—(CH₂)_(n1)—(CR²R³)_(n2)—, wherein R² and R³ are selected from hydrogenand fluorine, provided that at least one of R² and R³ in each —(CR²R³)—is fluorine, n1 is an integer of 0 to 10, and n2 is an integer of 1 to10.

Y is an anionic group, which may be SO₃, CO₂, NHSO₃, or O.

G⁺ represents a cationic portion of the photoacid generator compoundhaving formula (I). In an embodiment, G⁺ may have formula (III), (IV),or (V):

wherein

X is I or S,

R^(h), R^(i), R^(j), R^(k) and R^(l) are unsubstituted or substitutedand are each independently hydroxy, nitrile, halogen selected fromfluorine, chlorine, bromine, and iodine, a C₁₋₃₀ alkyl group, a C₁₋₃₀fluoroalkyl group, a C₃₋₃₀ cycloalkyl group, a C₁₋₃₀ fluorocycloalkylgroup, a C₁₋₃₀ alkoxy group, a C₃₋₃₀ alkoxycarbonylalkyl group, a C₃₋₃₀alkoxycarbonylalkoxy group, a C₃₋₃₀ cycloalkoxy group, C₅₋₃₀ acycloalkoxycarbonylalkyl group, a C₅₋₃₀ cycloalkoxycarbonylalkoxy group,a C₁₋₃₀ fluoroalkoxy group, a C₃₋₃₀ fluoroalkoxycarbonylalkyl group, aC₃₋₃₀ fluoroalkoxycarbonylalkoxy group, a C₃₋₃₀ fluorocycloalkoxy group,a C₅₋₃₀ fluorocycloalkoxycarbonylalkyl group, a C₅₋₃₀fluorocycloalkoxycarbonylalkoxy group, a C₆₋₃₀ aryl group, a C₆₋₃₀fluoroaryl group, a C₆₋₃₀ aryloxy group, a C₆₋₃₀ fluoroaryloxy group, ora C₂₋₃₀ acetal group comprising —O—C(R¹¹R¹²)—O— (wherein R¹¹ and R¹² areeach independently hydrogen or a C₁₋₃₀ alkyl group), each of which isunsubstituted or substituted;

wherein at least one of R^(i), R^(j), R^(k) and R^(l) is optionallysubstituted with an acid-sensitive group, a polymerizable group, or acombination thereof;

Ar¹ and Ar² are independently C₁₀₋₃₀ fused or singly bonded polycyclicaryl groups;

wherein X is S or I;

p is an integer of 2 or 3,

wherein when X is I, p is 2, and wherein when X is S, p is 3,

q and r are each independently an integer from 0 to 5,

u is an integer from 0 to 1, wherein when u is 0, X is I, and whereinwhen u is 1, X is S, and

s and t are each independently an integer from 0 to 4.

In formula (II), when X is S, one of the R^(c) is optionally attached toone adjacent R^(c) to form a ring.

In formulae (III), (IV), or (V), at least one of R^(h), R^(i), R^(j),and R^(k) may be an acid-cleavable group. In an embodiment, theacid-cleavable group may be (i) a tertiary C₁₋₃₀ alkoxy (for example, atert-butoxy group), a tertiary C₃₋₃₀ cycloalkoxy group, a tertiary C₁₋₃₀fluoroalkoxy group, (ii) a tertiary C₃₋₃₀ alkoxycarbonylalkyl group, atertiary C₅₋₃₀ cycloalkoxycarbonylalkyl group, a tertiary C₃₋₃₀fluoroalkoxycarbonylalkyl group, (iii) a tertiary C₃₋₃₀alkoxycarbonylalkoxy group, a tertiary C₅₋₃₀ cycloalkoxycarbonylalkoxygroup, a tertiary C₃₋₃₀ fluoroalkoxycarbonylalkoxy group, or (iv) aC₂₋₃₀ acetal group including moiety —O—C(R¹¹R¹²)—O— (wherein R¹¹R¹² areeach independently hydrogen or a C₁₋₃₀ alkyl group).

Also, in formulae (III), (IV), or (V), at least one of R^(h), R^(i),R^(j), and R^(k) may be a polymerizable group. A polymerizable group maybe a group including a carbon-carbon double bond or carbon-carbon triplebond. In an embodiment, the polymerizable group may include as part orall of its structure C₂₋₁₂ alkenyl, C₂₋₁₂ alkynyl, acryloyl,2-(C₁₋₁₂-alkyl)acryloyl, 2-(C₁₋₁₂-fluoroalkyl)acryloyl, 2-cyanoacryloyl,or 2-fluoroacryloyl.

The photoacid generator compound having formula (I) may include both anacid-cleavable group and a polymerizable group.

The photoacid generator compound having formula (I) may include at leasttwo iodine atoms, which may be located in the cation, the anion, orboth. In formula (II), when X is S (i.e., when the cation is a sulfoniumcation), the photoacid generator compound may include at least twoiodine atoms. The at least two iodine atoms may be located in thesulfonium cation, the anion, or both. In formula (II), when X is I(i.e., when the cation is an iodonium cation), the photoacid generatorcompound may include at least one iodine atom in addition to thepositively charged iodine atom of the iodonium cation. The at least oneiodine atom may be located in the iodonium cation, the anion, or both.In some embodiments, the photoacid generator compound may include 2, 3,4, 5, 6, 7, 8, 9, or 10 iodine atoms. In other embodiments, G⁺ mayinclude one, two, three, four, or five iodine atoms.

Specific examples of the anionic portion of the monomer having formula(I) may be represented by the following chemical formulae:

Specific examples of the cationic portion of the monomer having formula(I) may be represented by the following chemical formulae:

Specific examples of the monomer having formula (I) may be representedby the following chemical formulae, but are not limited thereto:

An embodiment of the present disclosure provides a photoresistcomposition including the above photoacid generator compound and acopolymer. The copolymer may include the acid-deprotectable monomerrepresented, the base-soluble monomer, and the lactone-containingmonomer.

The acid-deprotectable monomer may be represented by formula (II):

In the formula (VI), R^(b) may independently be H, an unsubstituted orsubstituted C₁₋₂₀ alkyl, an unsubstituted or substituted C₃₋₂₀cycloalkyl, an unsubstituted or substituted C₆₋₂₀ aryl, or anunsubstituted or substituted C₇₋₂₀ aralkyl, and each R^(b) may beseparate or at least one R^(b) may be bonded to an adjacent R^(b) toform a cyclic structure. In an embodiment, the tertiary group includingR^(b) in formula (VI) may be a t-butyl group. In another embodiment, theformula (VI) may include cycloalkyl structures, which incorporate two ormore R^(b) groups, such as 1-methylcyclopentyl, 1-ethylcyclopentyl, and1-methylcyclohexyl, and the like.

Exemplary acid deprotectable monomers of the formula (VI) may include:

or a combination including at least one of the foregoing, wherein R^(a)is H, F, C₁₋₆ alkyl, or C₁₋₆ fluoroalkyl.

The base-soluble monomer may be represented by formula (VII):

In the formula (VII), Q₁ may be an ester-containing or non-estercontaining group selected from an unsubstituted or substituted C₁₋₂₀alkyl, an unsubstituted or substituted C₃₋₂₀ cycloalkyl, anunsubstituted or substituted C₆₋₂₀ aryl, and an unsubstituted orsubstituted C₇₋₂₀ aralkyl group. In an embodiment, where an ester isincluded, the ester may form a connective link between Q₁ and the pointof attachment to the double bond. In this way, where Q₁ is an estergroup, the formula (VII) may be a (meth)acrylate monomer. In anotherembodiment, where an ester is not included, Q₁ may be aromatic, so thatthe formula (VII) may be, for example, a styrenic monomer or vinylnaphthoic monomer. Q₁ may be fluorinated or non-fluorinated. Further inthe formula (VII), a may be an integer of 1 to 3, for example, a may be1 or 2.

Also in the formula (VII), W may be a base-reactive group comprising atleast one selected from —C(═O)—OH; —C(CF₃)₂OH; —NH—SO₂—Y¹ where Y¹ maybe F or C₁₋₄ perfluoroalkyl; —OH; and an adduct of any of the foregoingwith a vinyl ether. In an embodiment, where Q₁ is non-aromatic (e.g.,where formula (VII) includes a (meth)acrylate structure having an esterlinked alkyl or cycloalkyl group Q₁), W may be —C(CF₃)₂OH. In anotherembodiment, where Q₁ is aromatic (e.g., where Q₁ is either ester-linkedor non-ester linked and is an aromatic group such as phenyl ornaphthyl), W may be OH or —C(CF₃)₂OH. It is contemplated that any of thebase-reactive groups may further be protected by an acid decomposableacetal leaving group (e.g., having a generic structure —O—CH(R′)—O—R″where R′ may be a methyl, ethyl, or other alkyl group) Such groups areadducts of a vinyl ether, such as, for example, ethyl vinyl ether,propyl vinyl ether, t-butyl vinyl ether, cyclohexylvinyl ether, the2-vinyloxyethyl ester of 1-adamantane carboxylic acid, 2-naphthoyl ethylvinyl ether, or other such vinyl ethers.

Exemplary base-soluble monomers having the formula (VII) may include:

or a combination comprising at least one of the foregoing, wherein R^(a)may be H, F, C₁₋₆ alkyl, or C₁₋₆ fluoroalkyl.

The lactone-containing monomer may be represented by formula (VIII):

In formula (VIII), L may be a monocyclic, polycyclic, or fusedpolycyclic C₄₋₂₀ lactone-containing group. Such lactone groups may beincluded to improve both adhesion of the polymer to a substrate, and tomoderate the dissolution of the polymer in a base developer. In anembodiment, L may be a monocyclic C₄₋₆ lactone which is attached to a(meth)acrylate moiety through a monocycle ring carbon; or L may be aC₆₋₁₀ fused polycyclic lactone based on a norbornane-type structure.

In an embodiment, a lactone-containing monomer may have formula (VIIIa):

wherein

R^(a) may be H, F, C₁₋₆ alkyl, or C₁₋₆ fluoroalkyl, R is a C₁₋₁₀ alkyl,cycloalkyl, or heterocycloalkyl, and

w may be an integer of 0 to 6.

It will be appreciated in formula (VIIIa) that R may be separate or maybe attached to the lactone ring and/or one or more R groups, and thatthe methacrylate moiety may be attached to the lactone ring directly, orindirectly through R.

Exemplary lactone-containing monomers of formulae (VIII) and (VIIIa) mayinclude:

In an embodiment, the copolymer may have the following structure:

The photoresist composition including the copolymer and the photoacidgenerator as disclosed herein may be used to provide a layer includingthe photoresist. A coated substrate may be formed from the photoresistcomposition. Such a coated substrate includes: (a) a substrate havingone or more layers to be patterned on a surface thereof; and (b) a layerof the photoresist composition over the one or more layers to bepatterned.

Substrates may be any dimension and shape, and are preferably thoseuseful for photolithography, such as silicon, silicon dioxide,silicon-on-insulator (SOI), strained silicon, gallium arsenide, coatedsubstrates including those coated with silicon nitride, siliconoxynitride, titanium nitride, tantalum nitride, ultrathin gate oxidessuch as hafnium oxide, metal or metal coated substrates including thosecoated with titanium, tantalum, copper, aluminum, tungsten, alloysthereof, and combinations thereof. Preferably, the surfaces ofsubstrates herein include critical dimension layers to be patternedincluding, for example, one or more gate-level layers or other criticaldimension layers on the substrates for semiconductor manufacture. Suchsubstrates may preferably include silicon, SOT, strained silicon, andother such substrate materials, formed as circular wafers havingdimensions such as, for example, 20 cm, 30 cm, or larger in diameter, orother dimensions useful for wafer fabrication production.

Further, a method of forming an electronic device includes (a) applying(casting) a layer of the above photoresist composition on a surface ofthe substrate; (b) pattern-wise exposing the photoresist compositionlayer to activating radiation; and (c) developing the exposedphotoresist composition layer to provide a resist relief image.

Applying may be accomplished by any suitable method, including spincoating, spray coating, dip coating, doctor blading, or the like.Applying the layer of photoresist is preferably accomplished byspin-coating the photoresist in solvent using a coating track, in whichthe photoresist is dispensed on a spinning wafer. During dispensing, thewafer may be spun at a speed of up to 4,000 revolutions per minute(rpm), preferably from about 200 to 3,000 rpm, and more preferably 1,000to 2,500 rpm. The coated wafer is spun to remove solvent, and baked on ahot plate to remove residual solvent and free volume from the film tomake it uniformly dense.

The casting solvent can be any suitable solvent known to one of ordinaryskill in the art. For example, the casting solvent can be an aliphatichydrocarbon (such as hexane, heptane, and the like), an aromatichydrocarbon (such as toluene, xylene, and the like), a halogenatedhydrocarbon (such as dichloromethane, 1,2-dichloroethane,1-chlorohexane, and the like), an alcohol (such as methanol, ethanol,1-propanol, iso-propanol, tert-butanol, 2-methyl-2-butanol,4-methyl-2-pentanol, and the like), water, an ether (such as diethylether, tetrahydrofuran, 1,4-dioxane, anisole, and the like), a ketone(such as acetone, methyl ethyl ketone, methyl isobutyl ketone,2-heptanone, cyclohexanone, and the like), an ester (such as ethylacetate, n-butyl acetate, propylene glycol monomethyl ether acetate(“PGMEA”), ethyl lactate, ethyl acetoacetate, and the like), a lactone(such as γ-butyrolactone, ε-caprolactone, and the like), a nitrile (suchas acetonitrile, propionitrile, and the like), an aprotic bipolarsolvent (such as dimethylsulfoxide, dimethylformamide, and the like), ora combination thereof. The choice of the casting solvent depends on aparticular photoresist composition and can be readily made by one ofordinary skill in the art based on knowledge and experience.

Pattern-wise exposure is then carried out using an exposure tool such asa stepper, in which the film is irradiated through a pattern mask andthereby is exposed pattern-wise. The method preferably uses advancedexposure tools generating activating radiation at wavelengths capable ofhigh resolution including EUV or e-beam radiation. It will beappreciated that exposure using the activating radiation decomposes thePAG in the exposed areas and generates acid and decompositionby-products, and that the acid or the by-products then effectuates achemical change in the polymer and nanoparticles (deblocking the acidsensitive group to generate a base-soluble group, or alternatively,catalyzing a crosslinking reaction in the exposed areas). The resolutionof such exposure tools may be less than 30 nm.

Developing the exposed photoresist layer is then accomplished bytreating the exposed layer to a suitable developer capable ofselectively removing the exposed portions of the film (where thephotoresist is a positive tone) or removing the unexposed portions ofthe film (where the photoresist is crosslinkable in the exposed regions,i.e., a negative tone). Preferably, the photoresist is a negative tone,based on a polymer having pendant and/or free acid groups or by-products(derived from bound or free PAG following irradiation) that inhibit thedissolution of the nanoparticles, and the developer is preferablysolvent based. A pattern forms by developing. The solvent developer canbe any suitable developer known in the art. For example, the solventdeveloper can be an aliphatic hydrocarbon (such as hexane, heptane, andthe like), an aromatic hydrocarbon (such as toluene, xylene, and thelike), a halogenated hydrocarbon (such as dichloromethane,1,2-dichloroethane, 1-chlorohexane, and the like), an alcohol (such asmethanol, ethanol, 1-propanol, iso-propanol, tert-butanol,2-methyl-2-butanol, 4-methyl-2-pentanol, and the like), water, an ether(such as diethyl ether, tetrahydrofuran, 1,4-dioxane, anisole, and thelike), a ketone (such as acetone, methyl ethyl ketone, methyl isobutylketone, 2-heptanone, cyclohexanone, and the like), an ester (such asethyl acetate, n-butyl acetate, propylene glycol monomethyl etheracetate (“PGMEA”), ethyl lactate, ethyl acetoacetate, and the like), alactone (such as γ-butyrolactone, ε-caprolactone, and the like), anitrile (such as acetonitrile, propionitrile, and the like), an aproticbipolar solvent (such as dimethylsulfoxide, dimethylformamide, and thelike), or a combination thereof. In an embodiment, the solvent developermay be a miscible mixture of solvents, for example, a mixture of analcohol (iso-propanol) and ketone (acetone). The choice of the developersolvent depends on a particular photoresist composition and can bereadily made by one of ordinary skill in the art based on knowledge andexperience.

The photoresist may, when used in one or more such pattern-formingprocesses, be used to fabricate electronic and optoelectronic devicessuch as memory devices, processor chips (CPUs), graphics chips, andother such devices.

Hereinafter, the present disclosure is illustrated in more detail withreference to examples. However, these examples are exemplary, and thepresent disclosure is not limited thereto.

EXAMPLES

The acronyms and chemical structures of monomers used in these examplesare presented in Table 1. The synthesis of the copolymer A designatedPPMA/aGBLMA/DiHFA/ECPPDPS F2 (36/48/11/5) is described in U.S. PatentPublication No. US 2017/0248844 A1 by Aqad et al. The synthesis of thesalt designated ECPPDBT Cl (5) was made as described in U.S. PatentPublication No. US 2014/0080058 A1 by Cameron et al.3,5-Diiodosalycilate lithium salt was purchased from Aldrich and used asreceived. The salt DTBPI Ac was purchased from Heraeus Precious MetalsNorth America Daychem LLC and used as received.

TABLE 1 Acronym Structure PPMA/aGBLMA/DiHFA/ECPPDPS F2 36/48/11/5(copolymer A)

ECPPDBT Cl (5)

ECPPDBT AdOH-TFBS

DTBPI Ac

Example 1: Photoactive Compounds Synthesis 1a) Photoacid GeneratorECPPDBT TIP-TFBA

The synthetic scheme for the photoacid generator designated ECPPDBTTIP-TFBA is summarized in FIG. 1. A suspension of 2,3,5-triiodobenzoicacid (1, 25 g) in 50 ml thionyl chloride was heated at 80° C. A clearsolution obtained after one hour. The heating at 80° C. was continuedfor an additional hour. The reaction mixture was cooled to roomtemperature and thionyl chloride was removed under reduced pressure. Theresulting product was dissolved in toluene, and the solvent wasevaporated to dryness under reduced pressure. The dry2,3,5-triiodobenzoyl chloride was added to a solution of 11.25 g4-bromo-3,3,4,4-tetrafluorobutanol in 100 mL of acetonitrile. Pyridine(5.20 g) was added and the mixture was stirred for 3 hours at roomtemperature. The solvent was evaporated to dryness under reducedpressure, and the residue was dissolved in 100 mL of dichloromethane,washed twice with 100 ml of 0.1N HCl and with 100 ml of water. Thedichloromethane was removed under reduced pressure and the crude productwas dissolved in 100 mL of acetonitrile. The acetonitrile solution wasadded to a mixture made of 17.2 g sodium dithionate and 12.5 g sodiumhydrogen carbonate and the mixture was stirred at 80° C. for 16 h. Thereaction was cooled to room temperature and the organic phase wasseparated and treated with 10 g of 30% hydrogen peroxide at 50° C. for 5h. The acetonitrile solution was concentrated to produce the crudesodium salt TIP-TFBS (3), which was used in the next step withoutfurther purification.

The crude sodium salt TIP-TFBS (3, 8.0 g) and 0.95 equivalents ofECPPDBT Cl (5) were mixed in 100 mL of dichloromethane and 100 ml ofwater and stirred at room temperature for 16 h. The organic phase wasseparated and washed twice with 100 mL of deionized water. The solventfrom the organic phase was completely removed under reduced pressure andpurified by flash chromatography using dichloromethane/acetone 3/1 byvolume. Fraction containing the product were combined, and the solventwas removed under reduced pressure to produce a white solid, which wasdissolved in 20 ml of dichloromethane. The solution was poured into 200ml of methyl t-butyl ether/heptane 1/1 by volume to produce 5.3 g purephotoacid generator compound ECPPDBT TIP-TFBS (10).

1b) Photoactive Quencher DTBPI DISA

The synthetic scheme for the photoactive quencher designated DTBPI DISAis summarized in FIG. 2. A solution made of DTBPI Ac (11.4 g, 25.2 mmol)and 3,5-diiodosalycilate lithium salt (10 g, 25.26 mmol) in 100 ml ofwater and 100 ml of dichloromethane was stirred at room temperature for6 h. The organic phase was separated and washed 5 times with 50 mL ofdeionized water. The organic phase was separated and the concentrated.The resulting residue was dissolved in 30 mL of acetone and poured into300 mL of heptane to precipitate the product DTBPI DISA, which wasfiltered and dried. Yield—14.2 g.

1c) Photoacid Generator IPDPS PFBuS

The synthetic scheme for the photoacid generator designated as IPDPSPFBuS is summarized in FIG. 3. Diphenyl sulfoxide (10 g, 49.44 mmol) andiodobenzene (10 g, 49 mmol) were added to 100 mL of Eaton's reagent, andthe mixture was stirred at room temperature overnight. The mixture waspoured into 200 g of crushed ice. Non-reacted organics were extractedwith methyl t-butyl ether and discarded, and 16.7 g of perfluorobutanesulfonate C₄F₉SO₃K) and 200 ml of dichloromethane were added to theaqueous phase. The mixture was stirred for 15 min at room temperatureand the CH₂Cl₂ was separated and washed 5 times with 100 mL deionizedwater. The organic phase was collected and the solvent was evaporated todryness under reduced pressure. The product was further dried underreduced pressure to produce the product IPDPS PFBuS. Yield—25.8 g.

1d) Photoacid Generator DTBPI 4IP-TFBS

The synthetic scheme for the photoacid generator designated as DTBPI4IP-TFBS is summarized in FIG. 4. To a solution of 4-iodobenzoylchloride (13.1 g, 49.16 mmol) and 4-bromo-3,3,4,4,-tetrafluorobutananol(11.0 g, 48.88 mmol) in 150 mL of tetrahydrofuran was addedtriethylamine (6 g), and the mixture was stirred at room temperature for16 hours. The resulting salt was filtered, and THF tetrahydrofuran wasremoved completely under reduced pressure. The resulting residue wasdissolved in 150 mL of dichloromethane and washed twice with 1 N aqueoussolution of hydrochloric acid, followed by one wash with 100 ml ofdeionized water. The organic phase was separated and the solvent wascompletely removed to produce the product 7 as an oily residue (yield19.5 g).

An aqueous solution made of sodium dithionate (7.5 g, 43.10 mmol) andsodium hydrogen carbonate (5.5 g, 65.5 mmol) was added to a solution ofcompound 7 (10 g, 22 mmol) in 200 mL of acetonitrile, and the mixturewas stirred at 75° C. for 16 hours. The mixture was cooled to roomtemperature and the lower, aqueous layer was removed. The upper, organiclayer was transferred into a flask. To the organic layer was addedhydrogen peroxide (10 g of 30 weight percent solution), and the mixturewas stirred at room temperature for 52 hours. The solution was filteredto remove salts, and the solvents were distilled off under reducedpressure to produce a gummy-like crude product. The crude product 9obtained from the previous step was suspended in 100 mL of water andmixed with a suspension of DTBPI Ac (10, 7.9 g, 17.5 mmol). Theresulting mixture was stirred at room temperature for 6 hours. Theorganic phase was separated, washed twice with 100 mL of deionizedwater, concentrated and poured into heptane to obtain the product DTBPI4IP-TFBS (11) which was collected by filtration and dried. Yield 7.5 g.

Example 2: Preparation of Photoresist Composition Formulations

Photoresist compositions containing copolymers comparative or inventivephotoacid generators were each independently formulated as summarized inTable 2. Component amounts in Table 2 are based on total solids,excluding solvents. The same molar PAG loading was used in the twoexamples.

The quencher was trioctylamine (TOA). The surfactant was a fluorinatedsurfactant obtained as POLYFOX™ PF-656.

TABLE 2 Photoresist Composition Copolymer PAG Quencher Surfactant 1Copolymer 49.0% ECPPDBT 2% 0.1% (comparative) A AdOH-TFBS 2 Copolymer66.4% ECPPDBT 2% 0.1% A TIP-TFBS

The formulations listed in Table 2 contained a 70:30 (w/w) mixture ofethyl lactate/methyl 2-hydroxyisobutyrate as a solvent, and resists wereprocessed at a soft bake of 110° C. for 90 seconds and a post-exposurebase at 100° C. for 60 seconds.

EUV Radiation Transmission Calculations

The effect of incorporating iodine atoms into photoacid generator onfilm transmittance at EUV radiation (13.5 nm) is exemplified by thetransmission calculation results. The transmissions at EUV exposure(13.5 nm) for the films made from photoresist compositions 1 and 2 werecalculated from the Center for X-Ray Optics at Lawrence BerkeleyNational Laboratory web site by inputting the calculated compositionmolecular formula and assuming a polymer density of 1.20 g/cm³ and filmthickness of 60 nm. Table 2 shows the calculated % transmission of thetwo compositions. Composition 2 that comprise the photoacid generatorECPPDBT TIP-TFBS, according to an embodiment of the present disclosureshows lower transmittance.

Contrast Curve

Contrast curve measurements with EUV exposure source (13.5 nm) wereobtained using a LithoTech Japan EUVES-9000 flood exposure tool. Theresist was spin-coated onto either an organic underlayer or a siliconwafer and baked at 110° C. for 90 seconds to form a 40-50 nm thickphotoresist film. The resist was exposed to an increasing dose of 13.5nm radiation in a step-wise manner, post-exposure baked at 100° C. for60 seconds, and developed with 0.26 N aqueous tetramethylammoniumhydroxide solution for 60 seconds to form a relief image pattern ofexposed and non-exposed areas. Thickness was measured at each exposedarea using a KLA Thermawave-7 ellipsometer and plotted vs. dose.Dose-to-clear values (E₀) were calculated at 10% or less remaining filmthickness. As can be seen from Table 3, photoresist composition 2,according to an embodiment of the present disclosure, exhibits smallerE₀ under EUV irradiation compared to photoresist composition 2, which isa comparative example.

TABLE 3 13.5 nm % Photoresist Transmittance at EUV E₀ Composition FT =60 nm (mJ/cm²) 1 (comparative) 71.35 1.5 2 67.64 1.0

Example 3: EUV Radiation Transmission Calculations

The transmissions at FIN exposure (13.5 nm) for films made fromcomposition examples were calculated from the for X-Ray Optics atLawrence Berkeley National Laboratory web site by inputting thecalculated composition molecular formula. Table 4 shows the calculated %transmissions for film made of photoactive compounds (shown in FIG. 5)at 60 nm film thickness, assuming film density of 1 g/cm³.

TABLE 4 13.5 nm % Photoacid Transmittance Example generator at FT = 60nm A (Comparative) PAG 1 77.06 B PAG 2 71.79 C PAG 3 68.32 D PAG4 66.02

Using these parameter, the transmission for a film made ofsulfonium-containing zwitterion (DPS-PTFBS) is 76.30% and the %transmission for a film made of tellurium-containing zwitterionDPTe-PTFB is 69.20%. This indicate the less transmission or moreabsorption for tellurium-containing zwitterionic compounds compared tosulfur analogues.

Table 5 shows the calculated % transmission for film made ofcompositions that include the base polymer and a photoacid generator (P1(shown in FIG. 5) at 60 nm film thickness, assuming film density of 1.2g/cm³. Comparative composition C1 includes polymer P1 and the iodinefree photoacid generator PAG1. The compositions I1 to I3, according toan embodiment of the present disclosure, include polymer P1 andiodine-containing photoacid generators PAG2, PAG3, and PAG4respectively. As can be seen from Table 5, less transmission is obtainedfor formulations that include PAG2, PAG3, and PAG4.

TABLE 5 PAG mol % in 13.5 nm % Transmittance Composition Polymer PAGcomposition at FT = 60 nm C P1 PAG1 10 74.18 (comparative) I1 P1 PAG2 1072.24 I2 P1 PAG3 10 70.53 I3 P PAG4 10 69.89

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A photoacid generator compound having formula (I):

wherein, in formula (I): “I” represents iodine; V is OR¹ or C(═O)OR¹,wherein R¹ is independently H or a substituted or unsubstituted C₁₋₃₀hydrocarbyl group optionally comprising 1 to 5 heteroatoms selected fromO, S, N, P, and F, and optionally comprising an acid-cleavable group, apolymerizable group, or a combination thereof; W is a single bond or agroup selected from —(C═O)O—, —O(C═O)—, —O(SO₂)—, —(SO₂)O—, —NH(SO₂)—,—(SO₂)NH—, —NH(CO)—, —(CO)NH—, —SO₂—, and —SO—; m is an integer of 0 orgreater; n is an integer of 0 or greater; L is a single bond, a groupselected from an unsubstituted C₁₋₂₀ alkylene group, an unsubstitutedC₁₋₂₀ heteroalkylene group, a substituted or unsubstituted C₃₋₂₀cycloalkylene group, and a substituted or unsubstituted C₃₋₂₀heterocycloalkylene group, a substituted or unsubstituted C₆₋₂₀ arylenegroup, and a substituted or unsubstituted C₇₋₂₀ aralkylene group, or agroup having formula —(CH₂)_(n1)—(CR²R³)_(n2)—, wherein R² and R³ areselected from hydrogen and fluorine, provided that at least one of R²and R³ in each —(CR²R³)— is fluorine, n1 is an integer of 0 to 10, andn2 is an integer of 1 to 10;

represents a monocyclic or polycyclic unsubstituted or substituted C₆₋₃₀arylene group or a monocyclic or polycyclic unsubstituted or substitutedC₃₋₃₀ heteroarylene group, wherein each “*” indicates a point ofattachment to a neighboring group or atom; G⁺ has formula (II):

wherein, in formula (II): X is S or I, each R^(c) is unsubstituted orsubstituted, halogenated or non-halogenated and is independently a C₁₋₃₀alkyl group; a polycyclic or monocyclic C₃₋₃₀ cycloalkyl group; apolycyclic or monocyclic C₄₋₃₀ aryl group, wherein when X is S, one ofthe R^(c) is optionally attached to one adjacent R^(c) to form a ring,and the photoacid generator compound having formula (I) comprises atleast two iodine atoms, and wherein when X is I, n is an integer of 1 orgreater, wherein when X is S, n is an integer of 0 or greater, providedthe photoacid generator having formula (I) comprises at least two iodineatoms, z is 2 or 3, wherein when X is I, z is 2, or when X is S, z is 3;and Y is SO₃, CO₂, NHSO₃, or O.
 2. The photoacid generator compound ofclaim 1, wherein W is a single bond or —(C═O)O—.
 3. The photoacidgenerator compound of claim 1, wherein L is a single bond or a grouphaving formula —(CH₂)_(n1)—(CR²R³)_(n2)—, wherein R² and R³ are selectedfrom hydrogen and fluorine, provided that at least one of R² and R³ ineach —(CR²R³)— is fluorine, n1 is an integer of 0 to 10, and n2 is aninteger of 1 to
 10. 4. The photoacid generator compound of claim 1,wherein

is a C₆ aryl group and n is 1, 2, 3, 4, or 5 when X═I, and n is 0, 1, 2,3, 4, 5 when X═S.
 5. The photoacid generator compound of claim 1,wherein the photoacid generator compound I comprises, two, three, four,or five iodine atoms.
 6. The photoacid generator compound of claim 1,wherein G⁺ has formula (III), (IV), or (V):

wherein X is I or S, R^(h), R^(i), R^(j), R^(k) and R^(l) areunsubstituted or substituted and are each independently hydroxy,nitrile, halogen selected from fluorine, chlorine, bromine, and iodine,a C₁₋₃₀ alkyl group, a C₁₋₃₀ fluoroalkyl group, a C₃₋₃₀ cycloalkylgroup, a C₁₋₃₀ fluorocycloalkyl group, a C₁₋₃₀ alkoxy group, a C₃₋₃₀alkoxycarbonylalkyl group, a C₃₋₃₀ alkoxycarbonylalkoxy group, a C₃₋₃₀cycloalkoxy group, C₅₋₃₀ a cycloalkoxycarbonylalkyl group, a C₅₋₃₀cycloalkoxycarbonylalkoxy group, a C₁₋₃₀ fluoroalkoxy group, a C₃₋₃₀fluoroalkoxycarbonylalkyl group, a C₃₋₃₀ fluoroalkoxycarbonylalkoxygroup, a C₃₋₃₀ fluorocycloalkoxy group, a C₅₋₃₀fluorocycloalkoxycarbonylalkyl group, a C₅₋₃₀fluorocycloalkoxycarbonylalkoxy group, a C₆₋₃₀ aryl group, a C₆₋₃₀fluoroaryl group, a C₆₋₃₀ aryloxy group, a C₆₋₃₀ fluoroaryloxy group, ora C₂₋₃₀ acetal group comprising —O—C(R¹¹R¹²) (wherein R¹¹ and R¹² areeach independently hydrogen or a C₁₋₃₀ alkyl group), each of which isunsubstituted or substituted; wherein at least one of R^(i), R^(j),R^(k) and R^(l) is optionally substituted with an acid-sensitive group,a polymerizable group, or a combination thereof; Ar¹ and Ar² areindependently C₁₀₋₃₀ fused or singly bonded polycyclic aryl groups;wherein X is S or I; p is an integer of 2 or 3, wherein when X is I, pis 2, and wherein when X is S, p is 3, q and r are each independently aninteger from 0 to 5, u is an integer from 0 to 1, wherein when u is 0, Xis I, and wherein when u is 1, X is S, and s and t are eachindependently an integer from 0 to
 4. 7. A photoresist compositioncomprising the photoacid generator compound of any of claims 1 to 6 anda copolymer.
 8. The photoresist composition of claim 7, wherein thecopolymer comprises the acid-deprotectable monomer represented byformula (VI), the base-soluble monomer represented by formula (VII), andthe lactone-containing monomer represented by formula (VIII):

wherein each R^(a) is independently H, F, C₁₋₁₀ alkyl, or C₁₋₁₀fluoroalkyl; each R^(b) is independently H, a substituted orunsubstituted C₁₋₂₀ alkyl group, a substituted or unsubstituted C₃₋₂₀cycloalkyl group, a substituted or unsubstituted C₆₋₂₀ aryl group, or asubstituted or unsubstituted C₇₋₂₀ aralkyl group, and each R^(b) isseparate or at least one R^(b) is bonded to an adjacent R^(b) to form acyclic structure; Q₁ is an ester-containing or non-ester containinggroup selected from a substituted or unsubstituted C₁₋₂₀ alkyl group, asubstituted or unsubstituted C₃₋₂₀ cycloalkyl group, a substituted orunsubstituted C₆₋₂₀ aryl group, and a substituted or unsubstituted C₇₋₂₀aralkyl group; W₁ is a base-reactive group comprising at least oneselected from —C(═O)—OH; —C(CF₃)₂OH; —NH—SO₂—Y¹ where Y¹ is F or a C₁₋₄perfluoroalkyl group; an aromatic —OH; and an adduct of any of theforegoing with a vinyl ether; a is an integer of 1 to 3; and L₁ is amonocyclic, polycyclic, or fused polycyclic C₄₋₂₀ lactone-containinggroup.
 9. A coated substrate, comprising: (a) a substrate having one ormore layers to be patterned on a surface thereof; and (b) a layer of aphotoresist composition of claim 7 over the one or more layers to bepatterned.
 10. A method of forming an electronic device, comprising: (a)applying a layer of the photoresist composition of claim 7 over asurface of the substrate; (b) pattern-wise exposing the photoresistcomposition layer to activating radiation; and (c) developing theexposed photoresist composition layer to provide a resist relief image.